¿Cuánta morfosintaxis en un diccionario histórico?

Does an historical dictionary have to give information on morphology and syntax? And more: which kind of morphological and syntactic features belong to the «history» of a single word and which kind to the linguistic system? Starting from these questions, this paper examines two examples taken from the Florentine of the fourteenth century: the reorganization of the third person plural simple past tense (§2) and the substitution of avere (to have) with essere (to be) as an auxiliary in reflexive constructions (§3). Only the latter, which concerns changes in the argument structure of each verb, is worth being mentioned in an historical dictionary. Finally, this paper examines some forms of lexicalization concerning multiword conjunctions (§4) and suggests how to represent them in a historical dictionary.